Newborn Body Basics

All you need to know about your baby's skin, hair, and more in his first weeks of life.

Every infant looks just about perfect to a brand-new mother. But the truth is that your little bundle of joy may actually arrive with some not-so-perfect features such as blemishes, yellowish skin, or a curiously shaped head. These oddities will probably disappear, but if they don't, they'll need medical attention. This guide will help you determine what's normal--and when you should take action.

Jaundice
Shortly after your baby is born, her skin may develop a yellowish tinge. Don't stress. This is a sign of jaundice, a condition that occurs in more than half of newborns. The pigment is due to bilirubin, which is the waste product that results from the breakdown of red blood cells. Normally, bilirubin is processed by the liver and then excreted. But because a newborn's liver function is relatively immature, the bilirubin can build up.

In most cases, once the liver gets into gear (usually in less than two weeks), your baby will lose this yellow hue. To help flush the bilirubin from your baby's system, your doctor may suggest that you increase the frequency of feedings. If your child is very yellow, however, or the condition persists beyond three weeks, she may benefit from phototherapy, which breaks down bilirubin in the skin into a form that can be excreted. Also, see your pediatrician if jaundice goes away and comes back--or if it develops weeks after birth--because this may mean liver problems.

Breast Buds
What should you do if you notice that your newborn (boy or girl) seems to be developing breasts? Relax. This--along with swollen genitals or discharge from the nipples or vagina--is due to the hormones you passed on to your baby during pregnancy. "The maternal hormones begin to dissipate once the umbilical cord is cut," says Rebecca Unger, M.D., a pediatrician at Children's Memorial Hospital, in Chicago. The swelling and discharge should disappear within your baby's first month. If the conditions persist, see your pediatrician.

Infant Acne
Baby acne is caused by two factors: the androgens you passed on to your baby during pregnancy, and his immature oil glands, which can get clogged. In a few weeks, hormone levels in your baby will subside, and the oil glands will mature, leaving your little one's skin clear--for at least the next decade. See your pediatrician if breakouts are accompanied by gastrointestinal problems, because this could signal an allergy.

Birthmarks
About one third of babies have salmon patches, flat pink marks that are actually dilated capillaries. More than 90 percent of Native American, Asian, Hispanic, and African-American babies have Mongolian spots--flat, bruiselike patches that are dense collections of skin cells. Less common are strawberry hemangiomas (raised red marks caused by widened blood vessels) and port-wine stains (large purple patches on the face due to an overgrowth of blood vessels). With the exception of port-wine stains, most birthmarks fade on their own during toddlerhood. Doctors recommend further evaluation when birthmarks are around the eye and interfere with vision, or if port-wine stains are large and involve the eyelid or forehead, a possible sign of eye or neurological problems.

Conehead
A newborn's skull is made up of separate bones that are not fully fused at birth. This makes it easier for your baby to squeeze through the birth canal. It also makes it more likely, however, that his skull will look pointed--especially if it took him a long time to make his way into the world. But this look won't last long. "The head should be more rounded in a day or so," says Joseph Gigante, M.D., associate professor of pediatrics at Vanderbilt Children's Hospital, in Nashville. And the bones will fuse gradually over the next several months (four to six months in the back of the head, and 12 to 18 months on the top).

Hair All Over
What's with the fuzz on your newborn's face, shoulders, and back? This thin, soft hair, called lanugo, is common: All fetuses grow it in the womb. It usually disappears by 36 to 40 weeks gestation, which explains why babies born early are especially likely to have it. Rest assured that the hair will fall out on its own by the time your baby is 4 months old. If it lasts beyond that though, talk to your pediatrician. Also, consult the doctor if your baby has a tuft of hair over her spine. This is not lanugo; it could be a sign of a neurological problem and should be investigated immediately.

For Boys Only: Three to 4 percent of full-term boys are born with undescended testicles. This happens when testicles--which develop in the fetal abdomen--fail to migrate into the scrotum as they normally do around the eighth month of pregnancy. The testicles usually make their way into position within three to six months. But if they haven't after a year, your doctor will need to intervene with hormone injections or surgery. An undescended testicle can compromise fertility and has an increased risk of becoming cancerous, says William A. Engle, M.D., a neonatologist in Indianapolis.

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